- This means changing the default behavior of not allowing the Root login (only with) -> allowing the root login

more info

* The default for the sshd_config(5) PermitRootLogin option has
changed from "yes" to "prohibit-password".

* PermitRootLogin=without-password/prohibit-password now bans all
interactive authentication methods, allowing only public-key,
hostbased and GSSAPI authentication (previously it permitted
keyboard-interactive and password-less authentication if those
were enabled).

With that configuration you cannot login in as root with a password. Use keys instead.

2. change "#PermitEmptyPasswords no" to "PermitEmptyPasswords yes" as in your case root does not have any password